This type of power wrench is previously well known and described in for instance European Patent No. 2 113 341. The ratchet type power wench described in this publication is provided with both a torque sensor and a rotational movement indicating angle encoder for retrieving data concerning a performed tightening operation to thereby enable approval or disapproval of the quality of a performed tightening operation. The torque sensor comprises a torsion load sensing strain gauge arrangement provided inside the output socket of the wrench, whereas the angle encoder comprises a code disc carried on a closed rear end portion of the output socket.
A problem concerned with the above described power wrench is that the output socket comprises a closed end portion specifically designed to carry the code disc of the angle encoder. Also the torque sensor arrangement requires a certain design of the output socket. This means in turn that the output socket could not be used as an open ended socket connectable to a screw joint or a screw joint engaging implement in alternative ways, for example to tighten right or left hand threaded screw joints or loosen previously tightened screw joints. This is a serious drawback since this type of wrench is rotated in one direction only. It would be possible, however, to remove the torque sensor arrangement from the output socket and use the pressure of the pressure medium fed to the actuator as a measure for the delivered output torque, but still the angle encoder arrangement makes it impossible to use the output socket for alternative ways of screw joint engagement and rotation.
Moreover, the closed end portion of the output socket carrying the code disc forms a limitation for the length of a protruding end portion of a screw when an engaging nut is run down and tightened on said screw by the power wrench.